Vladislav Lavrovsky works long hours in a university lab, studies science at the University of Calgary and is trying to develop bacteria that will chew up pollutants. All this, and he's only 17.

As Johan Gilchrist and a team of researchers ascended Sabancaya — an active volcano in the Andes of southern Peru — the volcanologist heard an alert he would never forget. "All of a sudden I hear on ...